Membrane-bound vesicles and particles including exosomes, ectosomes, microvesicles, and secretory lysosomes are recognized as means for transportation along non-classical secretory pathways. Various types of cells, such as cancer and immune cells, have been shown to release diverse vesicles so as to mediate cell-to-cell communications. Although secreted vesicles as above are defined differently depending on their biogenesis, secretory mechanisms, and functions, the classification of these particles is not clearly defined (established) as of now.
Aminoacyl-tRNA synthetase (ARS) is an enzyme that attaches a specific amino acid onto its corresponding tRNA. In higher organisms, the aminoacyl-tRNA synthetases include 23 types of enzymes, including three types involved in the formation of multisynthetase complex, such as AIMP1(p43), (AIMP2)p38, and (AIMP3)p18, besides 20 types of enzymes according to the respective kinds of amino acids. Except for the enzymes involved in the formation of multisynthetase complex, some enzymes are present in a free form. The aminoacyl-tRNA synthetases have been recently reported to have basic functions and various other activation functions under particular environments, one of which is an effect of promoting an apoptosis of particular cancer cells by glycyl-tRNA synthetase (GRS), leucyl-tRNA synthetase (LRS), isoleucyl-tRNA synthetase (IRS) and the like.
However, their apoptosis-inducing activity has been known, while their secretory mechanisms have still not been revealed.